Both rectifiers and transistors are essential components in high-voltage power electronics applications, for example, switching-mode power supplies and many forms of drive circuits. Rectifiers are commonly used to convert an Alternating Current (AC), which periodically reverses direction, to Direct Current (DC), which flows in a single direction. The respective conversion process is known as rectification. Rectifiers have various types including semiconductor diodes and Silicon-Controlled Rectifiers (SCRs).
In semiconductor technology, due to their characteristics, Group III-Group V (or III-V) semiconductor compounds are used to form various integrated circuit devices, such as high power field-effect transistors, high frequency transistors, or High Electron Mobility Transistors (HEMTs). A HEMT is a field effect transistor incorporating a junction between two materials with different band gaps (i.e., a heterojunction) as the channel instead of a doped region, as is generally the case for Metal-Oxide Semiconductor Field-Effect Transistors (MOSFETs). In contrast with the MOSFETs, the HEMTs have a number of attractive properties including high electron mobility, the ability to transmit signals at high frequencies, etc.
From the application point of view, Enhancement-mode (E-mode) HEMTs have many advantages. E-mode HEMTs allow for the elimination of negative-polarity voltage supply, and, therefore, the reduction in the circuit complexity and cost. Despite the attractive properties noted above, a number of challenges exist in connection with developing III-V semiconductor compound-based devices. Various techniques directed to configurations and materials of these III-V semiconductor compounds have been implemented to try and further improve transistor device performance.
For rectifiers, two-terminal power rectifiers with low forward turn-on voltages, low on-resistance, and high reverse breakdown voltages (BV) are desirable in high-voltage power electronics, e.g. in switching-mode power supplies and power factor correction circuits. Low on-state resistance and short reverse recovery time, for a given off-state breakdown voltage, are important for power conversion efficiency.
Various efforts have been made to improve the performance of power rectifiers. Some proposed structures include Junction Barrier Schottky diodes, Merged p-i-n Schottky (MPS) diodes, and synchronous rectifiers. Other proposed rectifiers include Schottky Barrier Diodes (SBDs) and p-i-n diodes on doped bulk GaN, which presents high-breakdown and low-on-resistance features.
However, since the epitaxial structures for SBD or p-i-n diodes are not compatible with the HEMT structures, the SBD or p-i-n diode rectifiers have not been successfully integrated with HEMTs (at least not without unacceptable performance loss). Although SBDs can be directly formed on AlGaN/GaN heterostructures, the series combination of the AlGaN/GaN heterojunction with the metal-AlGaN Schottky barrier results in higher turn-on voltages and higher on-resistances.